In recent years, the concrete floor industry has experienced an increasing demand for extremely flat floors (generically known as superflat floors) which are suitable for automated high level warehousing applications. Floor surface height deviations often cause vibrational damage to automated fork and turret trucks traveling upon the floor and also reduce the productivity of stacking cranes installed within the warehouse. Variations in floor height may also adversely affect the ability of automated equipment to locate and retrieve items from their respective storage places within a warehouse. The industry is currently attempting to adopt standards and specifications for floor flatness and is also trying to establish apparatus and methods suitable for measuring floor flatness to ensure compliance with such existing and future standards.
Heretofore, three basic categories of prior art apparatus and methods for measuring floor flatness have been utilized in the art, i.e., manual systems, semi-automatic systems and fully automatic systems.
The manual systems have typically comprised either an engineer's level and rod apparatus or a level straight edge with a sliding dial gauge mounted at right angles to the straight edge. Floor measurements indicated on the rod or from the dial gauge are obtained and then manually plotted.
The more recent semi-automatic systems have generally comprised apparatus having a pair of spaced apart wheels adapted to travel along a selected path upon a concrete floor surface. These systems include a sensor adapted to measure the height differential between the two wheels along the concrete floor. Examples of such prior art semi-automatic systems are the Analog Profileograph apparatus manufactured by Edward W. Face Company and an analog measuring apparatus manufactured by Mr. Ralph McLean of Fullerton, Calif.
Although such prior art manual and semi-automatic measuring systems have proven generally effective in the past, they possess inherent deficiencies which detract from their overall effectiveness and widespread use in the industry. The foremost deficiency of the manual prior art systems has been the extreme labor intensiveness of conducting measurements, often requiring a pair of skilled surveyors to be maintained upon the job site for prolonged durations. Further, such manual systems, although providing a true height reading along the floor surface, have necessitated the accumulation of height readings at only selected locations on the floor surface, with later interpolation of the measurement data to derive a height profile for the entire surface area of the floor. As will be recognized, such interpolation inherently introduces inaccuracies into the measurement results, which in superflat floor applications is oftentimes unacceptable.
The prior art semi-automatic systems, although typically not requiring significant interpolation of data results, have proven to be extremely expensive, and further require skilled operating technicians to be utilized upon the job site. Further, such semi-automatic systems have heretofore failed to provide a true height profile of the floor surface, but rather have only yielded a relative height differential throughout the surface area of the floor. In addition, current semi-automatic devices pose many anomalies associated with the data representation of absolute surface heights and many such systems have failed to provide the slope or level measurements of the floor.
A recent semi-automatic sensor beam device comprises a rigid beam supported upon the measurement surface at opposite ends thereof, and includes means to permit the rapid leveling of the beam into a level horizontal plane or axis. A height sensor is carried for transport along the beam and is adapted to contact the measurement surface. The sensor and transport mechanism generate height and position signals which may be processed by a microprocessor and printed or plotted to yield a true height profile of the measurement surface throughout the length of the beam.
A recent automatic single axis transport trolley device comprises the use of a trolley having a pair of wheels adapted to contact and travel upon the surface to be measured. A pair of optical sensors are mounted upon servo units attached adjacent each of the contact wheels and are adapted to track an optical beam utilized to generate a reference plane, axis or datum. During travel of the trolley along the surface, variations in the surface height from the optical reference plane are detected by the optical sensors which output signals that may be similarly processed to print and plot the true height profile of the measured surface.
A recent automatic dual axis transport trolley apparatus comprises a trolley which may be transported along the length of the surface to be measured and basically combines the structure of the semi-automatic beam sensor and fully automatic single axis embodiments to permit, in a step and repeat fashion, simultaneous sensing, printing, and plotting of the true surface height profile along both a transverse and longitudinal coordinate axis.
It is known to utilize an inclinometer so as to obtain such floor height measurements. The inclinometer provides measurements of the slope of the floor at selected points along a survey line. Measurements from a plurality of generally parallel survey lines are used to construct a profile of relative floor height measurements, so as to define the flatness of the floor.
One such prior art device is disclosed in U.S. Pat. No. 4,748,748 issued on Jun. 7, 1988 to Kirven and entitled, METHOD AND APPARATUS FOR MEASURING HEIGHT VARIATIONS ON A FLOOR SURFACE, the contents of which are hereby incorporated by reference.
However, although such contemporary devices are generally suitable for the intended purpose, they suffer from inherent deficiencies which detract from their overall usefulness and desirability. More particularly, the accuracy of contemporary devices has not heretofore attained a desired level. Further, various procedures have been developed in an attempt to improve the accuracy of such contemporary devices. The practice of these procedures adds to the complexity of the measurement process. Thus, the practice of such procedures substantially increases the time required to complete the measurement process, and is therefore costly and undesirable.
For example, inaccuracies in measurements when using an inclinometer to measure floor flatness occur when the measurement device is first started in motion, or when it is stopped and then restarted during the measurement process. When the measurement device is initially started, or is restarted, the inclinometer experiences acceleration which results in inaccurate measurements provided thereby, i.e., false slope readings due to the inertia of the sensor mass thereof. Similarly, when the measurement device is stopped, i.e., its forward motion is halted, the inclinometer experiences a deceleration which also inherently causes it to provide inaccurate readings. In an attempt to overcome the problem of inaccurate inclinometer readings due to accelerations and decelerations experienced thereby, contemporary practice dictates that the device be brought up to a constant velocity before such measurements are commenced and that any measurements taken when the device is not moving at the desired constant velocity are considered invalid.
Of course, this necessitates that the device be given a head start prior to the survey line defining the region upon which measurements are to be made, and that in the event of stoppage during the measurement process, the device be restarted a sufficient distance behind the stopping point so as to allow it to resume the desired constant velocity prior to continuing the measurement process.
Additionally, offset errors are introduced into the measurement process due to various mechanical inaccuracies inherent in the use of inclinometers and also due to various floor anomalities. Contemporary practice dictates that two runs or sets of measurements be taken, in opposite directions with respect to one another, so as to substantially cancel the effect of such offset errors. As such, a first set of floor height measurements are taken in a first direction along a survey line, and then the measurements are repeated in the opposite direction. Thus, the effects of mechanical deficiencies within the inclinometer, as well as floor anomalities, tend to be of opposite signs and thus cancel each other among the two runs, when the results of each set of measurements are combined.
Further, making two such runs facilitates tying the beginning of the runs to the end thereof so as to further improve measurement accuracy. Tying the beginning of the runs to the end thereof reduces cumulative errors by making the elevation at the beginning of the runs equal to the elevation at the end thereof, since the beginning and end of the runs is at the same location. For example, if we assume that the relative elevation at the beginning of the two runs is zero and that the measured elevation at the end of the two runs, as provided by the inclinometer, is one inch, then one inch of elevation error has clearly accumulated within the device since the beginning and end of the two runs are at the same location. All of the measurements along both the forward and return runs are then altered or normalized proportionally, according to the length of the distance traveled, so as to cause the ending elevation to assume its true value of zero inches of elevation relative to the starting point. Thus, the elevation one quarter of the total distance traveled would be reduced by one quarter of the total accumulated error, which is one quarter of an inch in this example. The elevation measurements taken at all other locations along the two runs are similarly modified, so as to completely eliminate accumulated error. In this manner, accumulated errors tend to be effectively canceled out and more accurate floor height measurements are thus provided.
However, as those skilled in the art will appreciate, the need to make two measurement runs, as opposed to a single run, is inefficient and costly.
As will be appreciated, such contemporary methodology essentially doubles the effort required to obtain an acceptably accurate set of floor height measurements. Thus, it would be beneficial to provide a means for attaining desired measurement accuracy while eliminating the need for making such redundant or double measurements.
Further the accuracy of contemporary devices is limited since such devices generally perform a single measurement approximately every twelve inches. While such a measurement interval has been found to be generally suitable, it does inherently permit the introduction of various inaccuracies. First, the interval of twelve inches is of sufficient length to allow undesirable deviations in floor level to exist between successive measurements.
For example, a dip might exist between two measurement points. The dip may be of sufficient depth so as to be undesirable in a superflat floor. Yet, the dip would go unmeasured since it occurs between measurement points. Such undesirable deviations are undetected according to contemporary methodology, since they occur within the twelve inch measurement interval, i.e., between the points where measurements are actually taken, and are thus not measured. It has been found that unmeasured floor height deviations which occur within the twelve inch interval can be of a sufficient degree so as to have undesirable effects upon equipment utilized in automatic warehouse applications. As such, it is believed that the measurement interval of twelve inches is too long.
Further it has been found that the taking of a single measurement for each measurement interval may provide a misleading indication of the true inclination at or near that point. Such an inaccurate reading may, for example, result when the precise point at which the measurement is made deviates substantially from the average slope in the immediate surrounding area. For example, a bump or dip occurring at the precise location of a measurement would result in a measurement which is not representative of the slope of the floor on either side of the dump or dip. Indeed, the measured slope may differ substantially from the average slope around the point of measurement. It is the average slope which is more representative of the slope of the floor within a particular area. Thus, minor irregularities in the floor surface may result in misleading or inaccurate slope readings when only a single measurement is performed for each measurement interval.
Further, such inaccuracies may result from the presence of dirt or other debris which affects the inclinometer measurement only at that particular measurement point. Such inaccurate measurements may also result from floor vibrations.
As such, it would be desirable to eliminate misleading or inaccurate inclinometer readings caused by such deviations from the average slope, dirt or debris, and/or floor vibration. It would further be desirable to provide a means for enhancing the accuracy of floor height measurements such that deviations intermediate the contemporary twelve inch measurement intervals are accurately and reliably indicated.
In view of the foregoing, it will be appreciated that although contemporary floor flatness measurement apparatus and methodologies have proven generally suitable for their intended purposes, they possess several inherent deficiencies which detract from their overall effectiveness and desirability.